This invention relates to a process for the preparation of dialiphatic, dialicyclic, or di(aryl-substituted aliphatic)carbonates. More specifically, the process relates to a process wherein dialiphatic, dialicyclic, or di(aryl-substituted aliphatic)alcohols are oxidatively carbonylated so as to prepare such carbonates.
The carbonates produced by this invention are well-known and are useful as synthetic lubricants, solvents, and chemical intermediates in the preparation of pharmaceutically active compounds and in the preparation of polymeric derivatives, for example, clear plastics.
Carbonates are typically produced by contacting phosgene with the appropriate alcohol. See Drake et al., J. Am. Chem. Soc., 52, 3720 (1960) and U.S. Pat. No. 2,379,250. The hydrogen chloride that is produced by this process is not easily eliminated and leads to the production of chlorine-containing products. Attempts to neutralize the hydrogen chloride, e.g., with an acid acceptor, have led to processing difficulties. Moreover, when secondary alcohols are employed, the competing reaction involving alkyl chloride formation is serious and necessitates the use of an acid acceptor.
Frevel et al., U.S. Pat. No. 3,642,858, disclose that carbonates can be prepared by reacting a cyclic alkylene carbonate with a nontertiary hydroxy-containing compound in the presence of a catalytic amount of an alkali metal.
Gaenzler et al., U.S. Pat. No. 3,952,045, disclose a method for preparing carbonates which comprises reacting an alcohol, with carbon monoxide and oxygen, in the presence of a catalyst comprising a copper salt, chloride or bromide, and an organic phosphorus compound.
Romano et al., U.S. Pat. No. 4,218,391, disclose the preparation of carbonates by reacting an alcohol with oxygen and carbon monoxide in the presence of a catalyst which is a salt of a metal belonging to Groups IB, IIB, and VIII of the Periodic Table; the least possible number of inorganic anions is desirable in order to reduce the acidity of the environment as far as possible. The salts of monovalent copper are preferred.
Stammann et al., U.S. Pat. No. 4,370,275, disclose a process for the preparation of carbonates wherein an alcohol is reacted with a mixture of molecular oxygen and carbon monoxide in the liquid phase in the presence of a catalyst containing copper, chemically bonded oxygen, chemically bonded halogen and at least one nitrogen base.
Cipriani et al., U.S. Pat. No. 3,980,690, disclose the preparation of a carbonate which comprises reacting an alcohol with oxygen and carbon monoxide in the presence of a catalyst in the heterogeneous phase by introducing the reactants into a reactor charged with a catalyst such as the complex of a system formed by copper and 4-vinylpyridine, causing the reactants to flow over the catalyst, and then withdrawing the products of the reaction and unconsumed reactants from the reactor. It is taught that in order to obtain the catalyst described in the invention, use may be made of salts of metals belonging to the IB, II and VIII Groups of the Periodic system. For instance, salts of metals selected from among copper, silver, gold, zinc, cadmium, mercury, iron and nickel. The most suitable anions, to which the metal ion is bound, are selected from halides, CN-, ClO.sub.4 - or complex ions of the BF.sub.4 - type and the like.
Perrotti et al., U.S. Pat. No. 3,846,468, describe a process for the preparation of carbonates which comprises reacting an alcohol with oxygen and carbon monoxide in the presence of a catalyst which is copper complexed with an inorganic molecule. The catalyst disclosed generally corresponds to the formula MX.sub.n L.sub.m wherein M is a metal of IB, IIB or Group VIII of the Periodic system, preferably copper, silver, gold, zinc, cadmium, mercury, iron, cobalt, nickel, that is, metals able to exist in two different valence conditions by means of redox reactions; X is an anion; and L is a neutral ligand. With the more suitable anions being halide ions, cyanate ions, hypochlorate ions, and complex anions of BF.sub.4 - and the like. The ligands are selected from the group consisting of organic bases such as pyridine, dipyridyl, imidazole, phenanthroline, alkyl or aryl phosphines, dimethyl sulfoxide, dimethylformamide, quinuclidine, carbon monoxide, suitable ligands are also the nitriles such as acetonitrile, cyanobenzene, and the bidentate ligands such as malonitrile, succinodinitrile, adiponitrile and the like.
Hallgren et al., U.S. Pat. No. 4,361,519, disclose a process for the preparation of carbonates which comprises contacting an alcohol, carbon monoxide, a Bronsted base, a Group VIIIB element, oxygen and a redox cocatalyst.
Hallgren et al., U.S. Pat. No. 4,360,477, disclose the preparation of alkyl carbonates by carbonylation of alkanols with carbon monoxide and oxygen at elevated temperatures in the presence of certain copper salts.
The processes described hereinbefore generally demonstrate slow kinetics and have poor selectivity towards the desired carbonates under conditions which are suitable for commercial processes. Furthermore, many of the processes result in the presence of metal salts, such as copper halide salts, being present during the process. Such metals salts are generally corrosive and create significant problems in processing.
What is needed is a process for the preparation of carbonates wherein the rate of reaction is reasonable, the selectivity towards carbonates is high and there are no corrosive elements present so as to create significant problems in processing.